"Although carbon atoms and silicon atoms are similar in structure, they are not identical. The silicon atom is quite a bit more massive than the carbon atom, and moreover, the chemical bonds in silicon-containing molecules are nowhere near as strong as those in organic molecules. Since it is the strength of these bonds that makes carbon-based life so versatile, it would seem difficult to have a silicon-based lifeform that could remain intact for any given length of time, except, perhaps only under a rather narrow range of conditions."So, Eldrad must live.
Nature Alan Hale in the Alamogordo Daily News considers the possibilities for the discovery of silicon based life. He's unconvinced: